Axial oil scoop for a gas turbine engine

ABSTRACT

An axial oil scoop for a gas turbine engine includes an outer surface with a concave profile, the outer surface includes a multiple of radial holes.

This application claims priority to U.S. Patent Appln. No. 61/770,155 filed Feb. 27, 2013.

BACKGROUND

The present disclosure relates to a gas turbine engine and, more particularly, to an axial oil scoop therefor.

Gas turbine engines, such as those that power modern commercial and military aircraft, generally include a compressor section to pressurize an airflow, a combustor section to burn a hydrocarbon fuel in the presence of the pressurized air, and a turbine section to extract energy from the resultant combustion gases. An appropriate number of hollow coaxial engine shafts extend along the longitudinal axis to interconnect the compressor and turbine sections.

An oil circuit supplies oil to a number of bearings that are strategically positioned at longitudinally spaced apart locations along the engine shafts. Bearing compartments enclose the bearing assemblies and maintain a volume of oil with an oil-air interface. Within the bearing compartments, oil is supplied under pressure and is sprayed at selected areas or diffused through bearing assemblies. The oil flow cools the bearing assemblies which develop heat under friction, lubricates the bearing assemblies, flushes out any foreign particles that develop and splashes within the bearing compartment to cool and lubricate internal surfaces before being withdrawn from the bearing compartment under the vacuum of a scavenge pump.

Various oil circulation mechanisms are provided in flow communication with each bearing compartment to supply a continuous flow of oil to the bearing compartment and scavenge spent oil from an outlet of the bearing compartment. Oftentimes, oil is supplied to bearing compartment components e.g., seals and bearings through a shaft mounted axial oil scoop.

SUMMARY

An axial oil scoop for a gas turbine engine according to one disclosed non-limiting embodiment of the present disclosure includes an outer surface with a concave profile, said outer surface includes a multiple of radial holes.

A further embodiment of the present disclosure includes, wherein said concave profile is directed toward an engine central longitudinal axis.

A further embodiment of any of the foregoing embodiments of the present disclosure includes, wherein said concave profile surrounds an engine central longitudinal axis.

A further embodiment of any of the foregoing embodiments of the present disclosure includes, wherein said outer surface is generally cylindrical.

A further embodiment of any of the foregoing embodiments of the present disclosure includes, wherein said outer surface is radially outboard an inner surface.

A further embodiment of any of the foregoing embodiments of the present disclosure includes, wherein said inner surface is angled with respect to an engine central longitudinal axis.

A further embodiment of any of the foregoing embodiments of the present disclosure includes, further comprising a back surface between said outer surface is radially outboard an inner surface.

A further embodiment of any of the foregoing embodiments of the present disclosure includes, wherein said back surface is radially directed.

A gas turbine engine according to another disclosed non-limiting embodiment of the present disclosure includes a shaft along an engine central longitudinal axis. A bearing at least partially supports the shaft. An axial oil scoop mounted to said shaft, said axial oil scoop includes an outer surface with a concave profile.

A further embodiment of any of the foregoing embodiments of the present disclosure includes, wherein said concave profile is directed toward an engine central longitudinal axis.

A further embodiment of any of the foregoing embodiments of the present disclosure includes, wherein said concave profile surrounds an engine central longitudinal axis.

A further embodiment of any of the foregoing embodiments of the present disclosure includes, wherein said outer surface includes a multiple of radial holes.

A further embodiment of any of the foregoing embodiments of the present disclosure includes, wherein said bearing is mounted around said axial oil scoop.

A method of lubricating a bearing that supports a shaft of a gas turbine engine according to another disclosed non-limiting embodiment of the present disclosure includes centrifugally directing oil through a multiple of radial holes in an axial oil scoop with a concave profile.

A further embodiment of any of the foregoing embodiments of the present disclosure includes spraying oil generally axially toward the axial oil scoop.

The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation of the invention will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, the following description and drawings are intended to be exemplary in nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiments. The drawings that accompany the detailed description can be briefly described as follows:

FIG. 1 is a schematic cross-section of an example gas turbine engine;

FIG. 2 is a schematic expanded cross-section of a portion of a bearing compartment with an axial oil scoop;

FIG. 3 is a perspective view of the axial oil scoop;

FIG. 4 is a cross-section of the axial oil scoop; and

FIG. 5 is an expanded cross-section of an oil capture surface of the axial oil scoop according to one disclosed non-limiting embodiment.

DETAILED DESCRIPTION

FIG. 1 schematically illustrates a gas turbine engine 20. The gas turbine engine 20 is disclosed herein as a two-spool turbofan that generally incorporates a fan section 22, a compressor section 24, a combustor section 26 and a turbine section 28. Alternative engine architectures might include an augmentor section and exhaust duct section (not shown) among other systems or features. The fan section 22 drives air along a bypass flowpath while the compressor section 24 drives air along a core flowpath for compression and communication into the combustor section 26 then expansion through the turbine section 28. Although depicted as a turbofan in the disclosed non-limiting embodiment, it should be understood that the concepts described herein are not limited to use with turbofans as the teachings may be applied to other types of turbine engines such as a low bypass augmented turbofan, turbojets, turboshafts, and three-spool (plus fan) turbofans wherein an intermediate spool includes an intermediate pressure compressor (“IPC”) between a Low Pressure Compressor (“LPC”) and a High Pressure Compressor (“HPC”), and an intermediate pressure turbine (“IPT”) between the high pressure turbine (“HPT”) and the Low pressure Turbine (“LPT”).

The engine 20 generally includes a low spool 30 and a high spool 32 mounted for rotation about an engine central longitudinal axis X relative to an engine static structure 36 via several bearing compartments 38. The low spool 30 generally includes an inner shaft 40 that interconnects a fan 42, a low pressure compressor 44 (“LPC”) and a low pressure turbine 46 (“LPT”). The inner shaft 40 drives the fan 42 directly or through a geared architecture 48 to drive the fan 42 at a lower speed than the low spool 30. An exemplary reduction transmission is an epicyclic transmission, namely a planetary or star gear system.

The high spool 32 includes an outer shaft 50 that interconnects a high pressure compressor 52 (“HPC”) and high pressure turbine 54 (“HPT”). A combustor 56 is arranged between the HPC 52 and the HPT 54. The inner shaft 40 and the outer shaft 50 are concentric and rotate about the engine central longitudinal axis X which is collinear with their longitudinal axes.

Core airflow is compressed by the LPC 44 then the HPC 52, mixed with fuel and burned in the combustor 56, then expanded over the HPT 54 and the LPT 46. The turbines 54, 46 rotationally drive the respective low spool 30 and high spool 32 in response to the expansion. The main engine shafts 40, 50 are supported at a plurality of points by the bearing compartments 38. It should be understood that various bearing compartments 38 at various locations may alternatively or additionally be provided.

In one example, the gas turbine engine 20 is a high-bypass geared aircraft engine with a bypass ratio greater than about six (6:1). The geared architecture 48 can include an epicyclic gear train, such as a planetary gear system or other gear system. The example epicyclic gear train has a gear reduction ratio of greater than about 2.3:1, and in another example is greater than about 2.5:1. The geared turbofan enables operation of the low spool 30 at higher speeds which can increase the operational efficiency of the LPC 44 and LPT 46 to render increased pressure in a relatively few number of stages.

A pressure ratio associated with the LPT 46 is pressure measured prior to the inlet of the LPT 46 as related to the pressure at the outlet of the LPT 46 prior to an exhaust nozzle of the gas turbine engine 20. In one non-limiting embodiment, the bypass ratio of the gas turbine engine 20 is greater than about ten (10:1), the fan diameter is significantly larger than that of the LPC 44, and the LPT 46 has a pressure ratio that is greater than about five (5:1). It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present disclosure is applicable to other gas turbine engines including direct drive turbofans, where the rotational speed of the fan 42 is the same (1:1) of the LPC 44.

In one example, a significant amount of thrust is provided by the bypass flow path due to the high bypass ratio. The fan section 22 of the gas turbine engine 20 is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet. This flight condition, with the gas turbine engine 20 at its best fuel consumption, is also known as bucket cruise Thrust Specific Fuel Consumption (TSFC). TSFC is an industry standard parameter of fuel consumption per unit of thrust.

Fan Pressure Ratio is the pressure ratio across a blade of the fan section 22 without the use of a Fan Exit Guide Vane system. The relatively low Fan Pressure Ratio according to one example gas turbine engine 20 is less than 1.45. Low Corrected Fan Tip Speed is the actual fan tip speed divided by an industry standard temperature correction of (“T”/518.7)^(0.5) in which “T” represents the ambient temperature in degrees Rankine. The Low Corrected Fan Tip Speed according to one example gas turbine engine 20 is less than about 1150 fps (351 m/s).

The bearing compartments 38-1, 38-2, 38-3, 38-4 in the disclosed non-limiting embodiment are defined herein as a front bearing compartment 38-1, a mid-bearing compartment 38-2 axially aft of the front bearing compartment 38-1, a mid-turbine bearing compartment 38-3 axially aft of the mid-bearing compartment 38-2 and a rear bearing compartment 38-4 axially aft of the mid-turbine bearing compartment 38-3.

Each of the bearing compartments 38-1, 38-2, 38-3, 38-4 include one or more bearings 60 (illustrated schematically) and one or more—typically two (2)—seals 62 (illustrated schematically). Various types of bearings 60 and seals 62 may be used herewith. The bearings 60 and seals 62 respectively support and interface with the shafts 40, 50 of the respective low spool 30 and high spool 32.

The seals 62 operate to seal a “wet” zone from a “dry” zone. In other words, regions or volumes that contain oil may be referred to as a “wet” zone and an oil-free region may be referred to as a “dry” zone. So, for example, the interior of each bearing compartment 38-1, 38-2, 38-3, 38-4 may be referred to as a wet zone that ultimately communicates with an oil sump while the region external thereto may be referred to as a dry zone. That is, the bearings 60 support the low spool 30 and the high spool 32 and the carbon seals 62 separate the “wet” zone from the “dry” zone to define the boundaries of each bearing compartment 38-1, 38-2, 38-3, 38-4. Although particular bearing compartments and bearing arrangements are illustrated in the disclosed non-limiting embodiment, other bearing compartments and bearing arrangements in other engine architectures such as three-spool architectures will also benefit herefrom.

With reference to FIG. 2, an axial oil scoop 68 (also shown in FIGS. 3 and 4) receives oil from a generally axial direction then redirects the oil generally radially to lubricate and cool the moving parts of the engine 20, such as the bearing 60. That is, the axial oil scoop 68 redirects generally axially directed oil toward a radial direction. In the disclosed non-limiting embodiment, the bearing 60 is mounted to the axial oil scoop 68. It should be appreciated that the axial oil scoop 68 may be located in various positions within the engine 20 and may be integral or mounted to the engine shafts 50.

The axial oil scoop 68 captures the oil sprayed (illustrated schematically by arrow L) from a nozzle 70. An oil capture surface 72 of the axial oil scoop 68 directs oil along a path 74 created thereby to a multiple of radial holes 75 for radial communication toward the bearing 60 or other component.

With reference to FIG. 5, the oil capture surface 72 is generally defined by a inner surface 76 that leads to a back surface 78 that then leads to an outer surface 80 and a forward hook surface 86. The inner surface 76 and the outer surface 80 generally surround the engine central longitudinal axis X. That is, the inner surface 76 and the outer surface 80 are generally cylindrical and are axially directed with respect to the engine central longitudinal axis X. The back surface 78 and the forward hook surface 86 are radially directed with respect to the engine central longitudinal axis X.

The inner surface 76 may be angled away from the engine central longitudinal axis X toward the back surface 78. That is, the inner surface 76 may form a frustroconical portion or cylindrical ramp that drives oil into the oil capture surface 72. The back surface 78 extends radially generally perpendicular to the engine central longitudinal axis X to back stop the oil. The outer surface 80 contains the radial holes 75. The forward hook surface 86 extends toward the inner surface 76 generally parallel to the back surface 78 to form a lip that operates to retain oil.

The outer surface 80 includes a concave profile 82 with the radial holes 75 at an apex thereof The concave profile 82 is directed inward toward the engine central longitudinal axis X. The concave profile 82 beneficially takes advantage of centrifugal forces on the oil to encourage the oil to enter the radial holes 75 more quickly to lessen the chance that oil may escape past the forward hook surface 86. The radial holes 75 may additionally be located within a recessed groove 84 to further direct the oil.

The radial holes 75 are located in the concave profile 82. As the outer surface 80 is generally concave with the radial holes 75 located at the apex thereof, centrifugal forces will tend to drive the oil toward the farthest point of the outer surface 80 relative engine central longitudinal axis X while the forward hook surface 86 retards oil from moving radially inward and potentially reducing efficiency for the axial oil scoop 68.

Increased axial oil scoop 68 efficiency reduces the oil flow quantity otherwise required as less oil is wasted. A reduction in required oil flow also reduces pumping losses and heat generation. This further benefits an overall reduction of engine parasitic losses.

Although the different non-limiting embodiments have specific illustrated components, the embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments.

It should be understood that relative positional terms such as “forward,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting.

It should be understood that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom.

Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure.

The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be understood that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content. 

What is claimed is:
 1. An axial oil scoop for a gas turbine engine comprising: an outer surface with a concave profile, said outer surface includes a multiple of radial holes.
 2. The axial oil scoop as recited in claim 1, wherein said concave profile is directed toward an engine central longitudinal axis.
 3. The axial oil scoop as recited in claim 1, wherein said concave profile surrounds an engine central longitudinal axis.
 4. The axial oil scoop as recited in claim 1, wherein said outer surface is generally cylindrical.
 5. The axial oil scoop as recited in claim 1, wherein said outer surface is radially outboard an inner surface.
 6. The axial oil scoop as recited in claim 5, wherein said inner surface is angled with respect to an engine central longitudinal axis.
 7. The axial oil scoop as recited in claim 6, further comprising a back surface between said outer surface is radially outboard an inner surface.
 8. The axial oil scoop as recited in claim 7, wherein said back surface is radially directed.
 9. A gas turbine engine comprising: a shaft along an engine central longitudinal axis; a bearing that at least partially supports said shaft; an axial oil scoop mounted to said shaft, said axial oil scoop includes an outer surface with a concave profile.
 10. The gas turbine engine as recited in claim 9, wherein said concave profile is directed toward an engine central longitudinal axis.
 11. The gas turbine engine as recited in claim 9, wherein said concave profile surrounds an engine central longitudinal axis.
 12. The gas turbine engine as recited in claim 9, wherein said outer surface includes a multiple of radial holes.
 13. The gas turbine engine as recited in claim 9, wherein said bearing is mounted around said axial oil scoop.
 14. A method of lubricating a bearing that supports a shaft of a gas turbine engine comprising: centrifugally directing oil through a multiple of radial holes in an axial oil scoop with a concave profile.
 15. The method as recited in claim 14, further comprising: spraying oil generally axially toward the axial oil scoop. 